Fuel burner control system



Nov. 29, 1938. H. T. SPARROW FUEL BURNER CONTROL SYSTEM Filed Jan. 25, 1956 Mom J-Z ube-rt T Sfzarraw H Patented Nov.- T29, 1938 UNITED STATES OFFICE to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn, a corporation oi Minnesota Application January 23, 1936, Serial No. 60,487

' 8 Claims.

My invention relates to a fuel burner control system, and more particularly to a control system for burners consuming a fluid fuel such as gas.

It is the usual practice with automatically controlled gas burning systems to employ a pilot for the ignition of the main burner. In certain cases this pilot is allowed to burn continuously while in other cases it is considered desirable to have the pilot burning only when the main burner is operating, and to provide special means for igniting the pilot, such as a spark gap or an auxiliary constantly burning pilot of a size having a relatively small gas consumption as compared with the main pilot. In the latter type of systems; i. e. where the main pilot is burning only when the main burner is to be lighted, the usual practice has been to provide two independent valves, one of which controls the supply of gas to the pilot and the other of which controls the supply of gas to the main. burner. These valves have each been provided with an independent actuating means. Since, however, the actuating means for these valves is responsible for a considerable part of the expense of such an installation, it is highly desirable to use as few valve actuating members as possible.

There is still another disadvantage to these previous systems. it is the usual practice in any fluid fuel burner control system wherein a pilot burner is employed for igniting the main burner to employ a safety pilot, that is a pilot burner with an associated safety pilot thermostat which is efiective to insure that the main burner valve is not opened until the safety pilot thermostat has been heated by reason of the pilot being ignited. in these prior systems no provision was made for the case wherein the main burner valve is momentarily closed for some reason, such as power failure, and wherein there is an attempt to open the main valve through the thermostat before the safety pilot thermostat has cooled. in such cases, the power failure or other cause, which has resulted in the main burner valve being momentarily closed, also results in the pilot burner valve being closed so that the, pilot is extinguished. If it is then possible to open the main burner valve due to the safety pilot thermostat still being hot, the very condition is produced which it is desired to avoid, that is, gas being admitted to the main burner before the pilot is lighted.

An object of the present invention is to provide a fuel burner control system of general utility but particularly applicable to the control of gas is a pilot burner ll.

burners wherein the pilot burner is not of the constantly burning type and wherein a single motor means is employed to actuate both the pilot valve and the main valve.

A further object of the present invention is to provide a system employing a single motor means for operating both a main fuel valve and a pilot fuel valve in which the motor means is effective to open the pilot valve immediately upon energizat'ion thereof but cannot open the main valve until the pilot burner has been lighted.

A further object of the present invention is to provide a gas burner control system wherein the gas from the pilot is ignited by a spark gap in which a single motor means is employed to actuate both the pilot valve and the main valve, and in which the spark transformer is efiective to prevent the motor from operating the main gas valve until the pilot burner has been lighted, and in which upon said pilot burner being lighted said'ignition means is rendered inoperative.

A further object of the present invention is to provide a 'gas burner control system of the type wherein the main burner valve is controlled by a safety pilot thermostat in which after the main valve has been open and then closed, it cannot be reopened, even though the safety pilot thermostat is still hot, until the pilot has been reignited.

A further object of the present invention is to provide a new and novel motorized valve of a type wherein a single motor actuates two different valves.

Further objects oi the present invention will be apparent from the following specification, claims and drawing, of which:

Figure l is a schematic view of my control system,

Figure 2 is a view partly in section of a body portion of my valve, and in which,

Figure 3 is' a sectional view of the pilot valve along the line 3-43 of Figure 2 on an enlarged scale relative to Figure 2.

Referring to Figure l, a gas burner of any conventional type is designated by the reference numeral 58. Associated with the gas burner it Both the main gas burner id and the pilot burner ii are connected to a gas main l2 and this connection is controlled by a valve 113 to be subsequentlydescribed.

The means for igniting the pilot burner comprises a plurality of electrodes M which are spaced apart to provide a spark gap therebetween. The electrodes M are connected to the opposite terminals of a secondary E5 of a stepup spark transformer l6. This spark transformer comprises. in addition to the high voltage secondary I5, a low voltage primary Ill.

The temperature sensitive element of a safety pilot thermostat is indicated by the reference numeral 1. This safety pilot thermostat may assume any desired form wherein, provision is made for the closure of one set of contacts when the pilot is cold and another set of contacts when the pilot is hot. As shown in a conventional manner in the drawing, the pilot thermostat comprises a bimetallic element 1 which when the pilot thermostat is cold engages a cold control 9 and when the pilot thermostat is hot engages a hot contact 8.

A step-down transformer I9 supplies power for the operation of my system. This transformer comprises a line voltage primary 20 and a low voltage secondary 2|. The line voltage primary 20 is connected to line wires 22.

The referencenumeral 23 is employed to designate a thermostat which controls the operation of my system. This thermostat may be of any type suitable for controlling operation of the burner according to any desired condition. Thus, the thermostat may conveniently take the form of a room thermostat located within the room or a space heated by the burner l 6. The thermostat 23 comprises a bimetallic element 26 which has attached thereto a contact arm 25 which is adapted to cooperate with contacts 26 and 2'17.

, As will be apparent from the drawing, the contact arm 25 is less widely spaced from contact 21 than from contact 26, so that upon movement of the contact arm 25 by the bimetallic element 24, the contact arm will first engage with contact 21 and then after a predetermined temperature change will engage with contact 26. As indicated by the legend, the bimetallic element is so arranged that the contact arm 25 is moved to the left upon a decrease in temperature.

As previously mentioned, the valve l3 controls the flow of gas both to the main burner l and to the pilot burner H. The motor means for actuating this valve is shown schematically in Figure 1, it forming no part of my present invention. As apparent from Figure 1, this motor means comprises a motor 28, having a rotor 29 and a field winding 30. The motor is connected through suitable reduction gearing 31 with a gear 32 which is secured to a shaft 34. Attached to the shaft 34 is a cam member 35 which cam member is adapted to cooperate with a switch arm 36. The cam 35 is mounted on the shaft 34 in any suitable manner to provide what is known as a slip friction connection; 1. e. a connection wherein the cam may be rotated against an opposing force of limited value but slips on the shaft when engaged by a positive stop. On its lower edge the cam is provided with a recess 3'! through which projects apin 38. The movement of the cam 35 is limited by the pin 38 engaging the opposite sides of the recess 31. The cam 35 is further provided with a heel portion 39 and a toe portion 40. The switch 36 is provided with a cam follower 4| which, with the parts in the position shown in the drawing, rests on the heel portion 39 of the cam 35. Upon rotation of the gear 32 in the direction in which it is driven by the motor, which direction is indicated by an arrow on the face thereof, the cam 35 is moved until the pin 38 engages the wall of a recess 31 which is opposite to the wall against which the pin 38 is resting in the position shown in the drawing, whereupon the cam slips on the shaft upon further rotation thereof. This movement of the cam 35 is suflicient to cause the cam follower M to ride up on the toe portion of the cam 35 with the result that the contact arm is moved into engagement with its associated contact 42. Upon the first movement of gear 32 in the opposite direction, the switch again moves to open position. The purpose of this switch and the cam actuating means is to control a holding circuit for the motor 28, as will be more apparent from a subsequent description of the operation of my system.

Located upon the gear 32 is a pin 44 which pin is adapted to engage the curved portion of a hook 45, which hook is pivotally connected with a lever 56. This lever is in turn pivotally mounted at 61 and connected to the stem 48 of valve l3. A pin 56 is adapted to engage the lever 46 and limit upward movement thereof and accordingly of the stem 48.

Referring now to Figure 2, the valve 63 is shown as consisting of a valve body i, having the usual inlet and outlet connections 52 and 53 and the usual partition 69.

The partition 39 is provided with an aperture to provide a valve opening and a valve seat. The valve stem 46 consists of two parts, 54 and 55, which are threadedly connected through a reduced shank portion 56 of member 55' which is in threaded engagement with a socket in the lower end of member 54. The lower end of the valve stem terminates in an enlarged head 51. Slidably mounted on the valve stem 48 at the lower end thereof is a main valve. This valve comprises a cup-shaped member 56 in which is located a disc, of some suitable valve facing material, 59. A washer 66 is located over the disc 59 and the members 58, 59 and 60 are held together through the clamping action of a sleeve 6i and a spring bearing member 62 threadedly engaged with each other. The sleeve 6| is provided at its lower portion with a recess 63 which is of a size to permit free movement of the head 57: therein. It will be seen that the stem 48 is free to move upwardly until the head 5'! engages.

the shoulder formed by the upper end of the recess 63 in sleeve 6|. After the head 51 has engaged the shoulder further upward movement of the stem 48 will cause upward movement of the valve.

Clamped between the two sections 54 and 55 of the valve stem is a sealing diaphragm 65, which diaphragm is clamped between two washers 66. The diaphragm 65 rests on its outer edge on the curved flange portion 61 of the spring bearing member 62. Located upon the upper surface of this diaphragm is a ring 68 against which bears a spring 69. This spring 69 bears at its opposite end against a bearing plate 16 attached to a closure member IL This closure member is secured to the valve body 5| through a screw thimble connection 12. Interposed between the closure plate H and the valve body 5| is a suitable gasket 13. The spring bearing plate I0 and the closure plate H are secured through rivets to a member 14, which member in turn supports the motor, the particular structure of which, and the particular manner of mounting of which, form no part of the present invention. The spring 69 serves to bias the main valve to a closed position against the seat. In doing so, the spring also serves to clampthe sealing diaphragm between the ring 68 and the flange 61 of the spring bearing member 62, thus serving to effectively valve casing 3|.

Secured to the member 14 is a sleeve I6, which sleeve serves to guide the valve stem 48 and also to form an abutment for a spring 11. The spring TI abuts at its upper end against a Washer 18 which in turn is in abutting engagement with the end of sleeve 16 and abuts at its lower end against the topmost of the two washers 66. The spring ll is relatively weak as compared with the spring 69 and isfor the purpose ofholding the valve stem 48 downwardly so as to maintain a valve stem 19 of the pilot valve 80 in a closed position. It will be noted that any upward movement of the valve stem 48 is resisted by the spring H but that the spring 69 does not resist such, upward movement until the stem 48 has been raised sufliciently to cause engagement of the head 51 with the shoulder in the lower portion of sleeve 58.

The construction of the pilot valve is most clearly shown in Figure 3. As shown in that figure, the pilot valve comprises a housing 8i which is in threaded engagement with a member 82 which member is in turn supported by the wall of the main valve housing 5I. The wall 5i is provided with a boss 83 which is internally threaded to support the member 82 and in turn support the pilot valve structure BI. The boss 83 is also internally threaded at its outer end to receive a pipe 85 leading to the pilot burner. The pilot valve housing BI is provided with upper and lower chambers 85 and 56. The upper chamber 85 constitutes the valve chamber proper and communicates with a longitudinally extending passage 81 in the member 82. The pilot valve stem IQ is provided with a conical valve surface 80 which seats against the upper edge of the pilot The pilot valve is biased to an open position by spring as which bears at its upper end against a flange 90 on the pilot valve stem l9, and at its lower end against a screwthreaded closure SI for the pilot valve casing 88. In the position shown in the drawing, which position is the closed position of both valves, the pilot valve stem I9 is held in its lowermost position by reason of the main valve stem 58 being urged downwardly by the spring H, which spring acts in opposition to the spring 89 associated with the pilot valve stem 19.

It will be apparent from the preceding description that the first initial upper movement of main valve stem t8 permits the spring 89 to move the pilot valve stem is upwardly opening the pilot valve. Due to the fact that the spring W is relatively weak, a relatively small force is necessary to cause such movement of the valve stem 58'. However, as soon as the head 57 of valve stem 08 engages the internal shoulder of sleeve 63 any further movement of the valve stem 88 must take place against the action of the spring 69, which spring is relatively strong. It is thus possible for the pilot valve to be opened when the motor is insufiiciently energized to lift the main valve.

Referring now to the operation of my system, let it be assumed that the temperature in the room falls to below, the desired value. At first the contact arm 25 will only engage the contact 2? but if the temperature continues to fall the contact arm 25 will be moved into engagement also with contact 20. Upon this taking place,

the following circuit is established through the motor winding 30: From the right-hand terminal of secondary 2I, through conductors I and MI,

primary I! of the ignition transformer, conductor I02, conductor I03, bimetallic element 1, contact 9, conductor I04, contact 26, contact arm 25, contact 21, conductor I05, field winding 30, and conductor I to the left-hand terminal of the secondary 2I. This causes the motor 28 to be energized with the result that the gear 33 is rotated in the direction of the arrow. -As prevlously explained, a very slight rotation of this gear and the resultant rotation of shaft 34 causes the switch arm 36 to be moved into engagement with the contact 02. Upon this taking place, the following holding circuit is established for the motor field winding 30: From the right-hand end of secondary 2i, through conductors I00-and IOI, the primary I! of the spark transformer. conductors I02 and I01, switch arm 36, contact 52, conductor I08, bimetallic element 24, contact arm 25, contact 211, conductor I05, field winding 30, and conductor I06 to the left-hand terminal of secondary 2|. It will be noted that the holding circuit just traced does not depend upon enagement of contact arm with contact 25 so ment of the bimetallic element i of the safety pilot thermostat with the cold contact 9 so that the circuit just traced is not interrupted upon.

the bimetallic element l moving out of engagement with the cold contact 9.

The holding and energizingcircuits just traced cause two things to happen. In the first place, the motor 28 is energized sumciently to cause the pin M to engage with the hook Q5 and to move the valve stem as upwardly against the action of the spring ll. As previously explained, this permits the pilot valve stem I9 to move upwardly in response to the action of the pilot valve spring 89 and to open the pilot valve. However, due to the presence of the primary of the spark transformer it in the motor circuit, the motor is not supplied with sumcient energy to move the main valve upwardly against the action of the spring 59. The result is that the valve stemilt is moved upwardly just sumciently to open the pilot valve and is stalled with the head 5? of the valve stem engaging the interior shoulder .of the sleeve 5!.

At the same time, the passage of current through the primary ll of the spark transformer It results in the energization of the ignition means so that a spark is' produced across the electrodes Id. The two conditions necessary for lighting of the pilot ill have now been established and under normal conditions the gas issuing from the pilot burner i I will be ignited by the spark across the two electrodes Hi.

If the pilot burner is lighted as the result of the establishment of combustion producing conditions, the bimetallic element 7 will be heated up causing the same to move out of engagement with cold contact 9 and into engagement with the hot contact 8. As soon as this takes place, the following new motor circuit is established: from the right-hand end of secondary 2i, through conductors I00 and H0, contact 8, bimetallic element 1, conductors I 03 and I01, switch arm 36, contact 52, conductor I00, bimetallic element 24, contact arm 25, contact 21, conductor I05, field winding 30 and conductor I06 to the left-hand terminal of secondary 2|. It will be noted that the circuit just traced does not contain the primary of the ignition transformer but in efiect constitutes a shunt thereacross. The establishment of this circuit, accordingly, has a two-fold result. In the first place, the-motor 28 is now supplied with sufficient energy to lift the main valve against the action of the spring 69, thus permitting gas to flow to, the main burner M, where it is ignited by the pilot burner ll. At the same time, the shunting of the primary I! of the ignition transformer l6 results in the ignition means being rendered inoperative and thus subtion of the gear 32 and shaft 34. If for any reason there is a power failure, the spring 69 will be effective to rotate the gear 32 in a counterclockwise direction to cause separation of switch arm 36 from contact 42. This separation of switch 36 from contact 42 opens both the motor circuit just traced and the circuit througlf the primary ll of the ignition transformer l6. Both the'main valve and the pilot valve remain closed until the bimetallic element 1 of the safety pilot thermostat has cooled ofi sufliciently to again move into engagement with contact 9 and reestablish the original energizing circuit through the primary of the ignition transformer and through the motor, which causes the previously described operation to be repeated so as to eventually cause the reigniting of the main burner. In this manner, it is impossible for the situation to occur wherein the main burner and'pilot burner valve are closed momentarily due to a power failure, and upon such power being restored both valves are opened without reestablishment of the circuit through the igniting means; With my system it is imperative that the entire system recycle upon even a momentary power failure, thus insuring that the pilot burner will be reignitedbefore. the main burner valve is opened.

It will be seen that a single motor is employed to operate both the pilot valve and the main valve; while at the same time provision is made for preventing the main valve being open until there is an assurance that the pilot burner has been ignited. Moreover, the means for preventing the motor from opening the main valve has a second function which is that of igniting the pilot burner. It will further be seen that the heating of the bimetallic element of the safety pilot thermostat as the result of the pilot burner being ignited results in both the ignition means being deenergized and, as-a consequence, in the motor being supplied with/sufficient power to open the main valve. I have thus provided a. very simple control circuit for a gas burner which employs a minimum of parts and which is absolutely safe in operation.

While I. have shown a specific embodiment of my invention, it will beunderstood that this is for purposes of illustration and that my invention is to be limited only by the scope of the appended claims. I

I claim as my invention:

1. In combination, a main fluid fuel burner, a

pilot burner, a pilot valve controlling the flow of fuel to said pilot burner, a main valve for controlling the flow of fuel to said main burner, an

electrically operated actuator, means connecting said actuator to said valves so as to cause successive opening of said valves in the order named,

a source of electrical energy, a circuit including said source of electrical energy and said actuator and operative to cause said actuator to move sufficiently to open said pilot valve, a switch, means for moving said switch to circuit closing position upon the presence of a flame at said pilot burner, and a second circuit including said 10 source of electrical energy, said actuator, and said switch, said last named circuit being operative upon being established to cause said actuator to move sufiiciently farther to open said main valve.

2. In combination, a main fluid fuel burner, a pilot burner, a pilot valve controlling the flow of fuel to said pilot burner, a main valve for controlling the flow of fuel to said main burner, an electrically operated actuator, means connect- 20 ing said actuator to said valves so as to cause successive opening of said, valves in the order named, yieldable means for biasing said pilot valve to closed position with a small force and for biasing said main valve to closed position 25 with a relatively large force, a source of electrical energy, a circuit including said source of electrical energy, said actuator, and impedance means having a sufficiently large value that said actuating means is supplied only with enough 30 energy to move said pilot valve to open positio" and means operative upon the ignitionof said; pilot burner to establish a shunt aroundsziid impedance means and thereby open said main valve.

3. In combination, a main fluid fuel burner, a pilot burner, a pilot valve controlling the fiow of fuel to said pilot burner, meansincluding an ignition transformer for igniting the fuel sup-' plied'to said pilot burner, a main valve for con- 40 trolling the flow of fuel to said. main burner, an electrically operated actuator, means connecting saidactuator to said valves so as to cause successive opening of said valves in the order named, yieldable means for biasing said pilot valve to 45 closed position with a small force and for biasing said main valve to closed position with a relatively large force, a source of electrical energy,

a circuit including said source of electrical, energy, said actuator, and the primary of said ig- 50 nition transformer, said primary having a sufficiently' large impedance that said actuating means is supplied only 'with enough energy to move said pilot valve to open position, and means operative upon the ignition of said pilot .burner to establish a shunt around said primary of said ignition transformer, and-thereby open said main valve.

4. In combination, first and second valves, a.

-motor for actuating both of said valves, means 50 operatively connecting said motor and said valves and effective upon movement of the motor in one direction to open first said first valve and then said second valve, means normally operative upon the opening of said first valve to establish a predetermined condition, and means for supplying energy to said motor, said means being operative to supply only suflicient energy to said motor to cause the same to niove said first valve to open position, until the condition normally established by the opening of said first valve has been brought about and then further to energize said motor to open said second valve.

5. In a fluid fuel burner control system, a

pilot burner, a v main burner, a pilot valve, a 7

main valve, means biasing said pilot valve to closed position with a relatively weak force and said main valve to closed position with a relatively strong force, a switch responsive to a controlling'condition, a second switch responsive to the temperature adjacent the pilot, ignition means comprising a spark transformer, a source of electrical energy, a circuit including said source of energy, said actuator, said first switch and said spark transformer, and a second circuit controlled by said second switch operative upon said pilot burner being ignited to establish a shunt around said ignition transformer and thereby open said main valve.

6. In combination, first and second valves, an electrically operated device for actuating both of said valves, means operatively connecting said device and said valves and efiective upon movement of said device in one direction to open first said first valve and then said second valve, means normally operative upon the opening of said first valve to establish a predetermined condition, a source of electrical energy, and a circuit including said source of electrical energy, said actuator, and impedance means of a value such as to provide just sufiicient current to said actuator device to cause the same to open the first valve but not the second valve, and means responsive to the condition normally established by the opening of said first valve to decrease the impedance of said circuit sufiiciently to cause opening of said second valve.

7. In a fluid fuel burner control system, a pilot burner, a main burner, a pilot valve controlling the flow of fuel to said pilot burner, a main valve controlling the flow of fuel to said main burner, a motor for actuating both oflsaid valves,

' means operatively connecting said motor and said valves and effective upon movement of the motor in one direction to open first said pilot valve and then said main valve, means to ignite said pilot burner when gas is admitted thereto by the opening of said pilot valve, means for supplying energy to said motor, said means being operative to supply only suflicient energy to said motor to cause the same to move said pilot valve to open position until the pilot has been ignited and then further to energize said motor to open said main valve.

8. In a fluid fuel burner control system, a pilot burner, a main burner, a pilot valve controlling the flow of fuel to said pilot burner, a main valve controlling the fiow of fuel to said main burner,

, vice to cause the same to open the pilot valve but not the main valve, and means responsive to the ignition of the pilot burner to decrease the impedance of said circuit sufficiently to cause opening of said main valve.

HUBERT T. SPARROW. 

